1. Field of the Invention
The present invention relates to methods for feeding monogastric animals, and more particularly to methods employing one or more hemicellulases, such as mannanase, that decrease the feed to gain, or increase the weight gain of animals fed a low caloric diet containing the enzyme.
2. Background
The world population continues to grow, but land for food production is finite. J. E. Cohen, Discover 17: 42-47, (1996). In order to keep up with the growing food demand, improvements in the utilization of food resources will be needed to maintain the current living standards. One approach to improved efficiency has been to enhance the digestion of feeds by the inclusion of enzymes. Chesson, A., Supplementary enzymes to improve the utilization of pig and poultry diets, pp 71-89, In Haresign, W. and D. J. A. Cole (eds), Recent Advances in Animal Nutrition--1987, Butterworths, London. Enzymatically aided digestion not only yields more meat per pound of feed, but also reduces the volume of manure and the disposal cost.
Four types of enzymes have been clearly recognized in the marketplace for their value in animal feeds. In diets that contain wheat, rye or triticale, the enzyme xylanase (endo-1,4-.beta.-D-xylanohydrolase, E.C. 3.2.1.8) has been shown to be beneficial. Pettersson et al., British Journal of Nutrition 62: 139-149, 1989). Wheat, rye and the wheat/rye hybrid triticale contain large amounts of the non-starch polysaccharide arabinoxylan in the endosperm cell wall. The arabinoxylan is not digested by monogastric animals, but is hydrolyzed by microbial xylanase.
A second example of an enzyme with widespread use in feeds is .beta.-glucanase [cellulase, endo-1,4-.beta.-D-glucan 4-glucanohydrolase E.C. 3.2.1.4; or endo-1,3-(1,3;1,4)-.beta.-D-glucan 3(4)-glucanohydrolase E.C. 3.2.1.6] that has been shown to be especially beneficial in diets containing barley and oats. Rotter et al., Nutrition Reports International 39: 107-120 (1989). As well as interfering with digestion, the glucan causes wet sticky manure that induces breast blisters on poultry. In practice, xylanase and .beta.-glucanase are applied together since arabinoxylan and glucan are both present in the cereal grains. Pettersson et al., Animal Production 51: 201-20 (1990).
The use of enzymes that cleave phosphorus from phytic acid (myo-inositol hexakisphosphate) is a third example of the beneficial use of enzymes in animal feed. Simons et al., British Journal of Nutrition 64: 525-540 (1990). In monogastric animals the phosphate is not released from phytic acid during digestion but is released in the manure through microbial action. Phytic acid has a significant content in typical feeds. Phosphate run-off becomes a problem during manure disposal by causing eutrophication of nearby rivers, lakes or bays. Incorporation of phytase lowers the phosphate content in the manure and significantly decreases the need to add phosphate salts to diets.
Mannanase is another enzyme that has gained commercial use in corn and soybean based diets. The decreased feed to gain, or increased weight gain, of monogastric animals fed a diet containing mannanase was unexpected in a diet based on corn. Until the discovery that bacterial endo-1,4-.beta.-D-mannanase (E.C. 3.2.1.78, also known as mannan endo-1,4-.beta.-mannosidase, see McCleary, B. V., .beta.-D-Mannanase, Methods in Enzymology 160: 596-609, 1988) increases feed efficiency in corn-soybean diets, enzymes were infrequently used in poultry or swine feeds grown on corn-soy diets. U.S. Pat. No. 5,429,828, incorporated herein by reference, teaches a method of improving the energy efficiency of hemicellulose-containing animal feed by means of adding a hemicellulase, specifically mannanase, to the diet.
The positive effect of adding endo-1,4-.beta.-D-mannanase on feeding efficiency was unexpected in a diet based on corn. In barley or oats that contain mixed-linked glucan, or wheat, rye and triticale that contain arabinoxylan, the anti-nutritive polymer represents a large percentage of the seed endosperm. In contrast, there is only a very minor content of polymers based on 1-4-.beta.-D-mannan in the common corn based diets. The main source of galactomannan in a typical corn based diet is the soybean meal (added primarily as a source of protein). Based on total sugar analysis and the percentage of non-starch polysaccharides, soybean meal could contain on the order of 1.3% mannan. Thus, a diet with 30% soybean meal would have only about 0.4% mannan polymer. The added energy that would be derived from complete digestion of this small percent of the diet cannot account for the large improvement seen in feed conversion and weight gain.
In many areas of the world, diet rations containing low metabolizable energy content are utilized. Diet rations in these countries are not supplemented with fat. As a consequence, there is a need to increase the energy efficiency for utilization of low fat diets. In developing or developed countries supplemental concentrated fat is being eliminated from the diet for health reasons. In addition, there are a surprising number of problems associated with the addition of concentrated fat to diet rations to increase the metabolizable energy (ME) content of the feed (Rouse, R. H., Fat quality, the confusing world of feed fats, pp 55-63 In: Proceedings of the 1994 Maryland Nutrition Conference, March 24-25, Baltimore, Md., University of Maryland Feed Industry Council, College Park, Md.).
Oxidation of unsaturated fatty acids in fat is known to lead to the formation of peroxides and free radicals. This in turn leads to the oxidation of feed nutrients and vitamins. There is also evidence available that indicates that high fat diets can lead to ventricular failure and/or ascites problems in broiler chickens (Mullins, T. M. and W. W. Saylor, Effects of a high fat diet on growth, right ventricular hypertrophy, right ventricular failure, and ascities formation in broiler chickens, Abstract 25, p 11, Southern Poultry Science Society, 16.sup.th Annual Meeting, Jan. 16-17, 1995, Atlanta, Ga.). Some sources of animal feed fat include restaurant waste fat that has been partially hydrogenated to create un-natural fatty acids with trans double bonds that can interfere with fertility, fatty acid metabolism and the energy value of the feed (Rouse, supra). Another issue is the presence of free fatty acids in commercial fats that can have adverse effects on production and may have an antimicrobial effect in the chicken gut (Rouse, supra). Blended fats are also frequently contaminated with PCBs, pesticide residues, heavy metals, and gossypol from cotton seed oil soapstock (Rouse, supra). Feed mill managers have to be vigilant about all these issues. It is well known that ingested fat (and materials dissolved in it like PCB) can be directly incorporated into the fat of the animal that consumes it and this may present important health risks. In addition, the fat in the animal rations can influence the taste of the meat. For example, more than 1% fish oil in chicken diets will cause a distinct fish-type odor in the meat or eggs (Lesson, S., and J. D. Summers, Chapter 2: Ingredient evaluation and diet formulation, (In) Commercial Poultry Nutrition, University Books, Guelph, Ontario, 1991). The effect of high fat content (especially animal fat) on product taste is another issue that some producers are beginning to pay close attention to. The ability to avoid the use of fat and still obtain the same productivity is of general interest.
There is a continuing need for higher efficiency in food production and the urgency of providing solutions will only increase with time. The use of high energy diets which include several percent of fat to promote efficient animal growth is not always possible or desirable due to the high cost of fat or vegetable oils, or limited amounts of available animal fat in some of the most highly populated parts of the world (for example in China and India). There is a basic inefficiency in using the available fat in feed. For example, in the chemical and soap industries the fat could have more value. Finally, there are a number of health issues and problems associated with the incorporation of exogenous concentrated fats in animal diets. These issues are a further indication that a reduced fat, reduced calorie, animal feed diet that maintains high feeding efficiency is urgently needed.
A need therefore exists for a method to increase the efficiency with which monogastric animals utilize feed rations that contain a low metabolizable energy content. Likewise, a need exists for a food ration that can be utilized efficiently by monogastic animals without addition of fat.